Method of making core plug



J1me 1961 M. c. VOISSEM METHOD OF MAKING CORE PLUG Filed Jan. 29, 1958 INVENTOR. Mae/0v C. VO/jSE/W BY 4476044, m1 m A I'T'OENEY5 2,988,032 METHOD OF MAKING CORE PLUG Marvin C. Voissem, Menasha, Wis., assignor to Badger Plug Company, Appleton, Wis., a corporation of Wisconsin Filed Jan. 29, 1958, Ser. No. 711,962 3 Claims. (Cl. 113-51)' This invention relates to a core plug.

I have discovered that without extra operations, considerable material can be saved, and interlocking engagement of the core plug in a paper roll core can be secured by stamping the blanks for the core plug from a strip of stock which is narrower than the maximum diameter of the blank so that the blank has fiat sides. When the core plug is formed from the blank, ribs are formed in its periphery in areas in which the ribs will intersect the notches resulting from the flattened sides of the blank. This exposes the ends of such ribs, with the result that the ribs do not offer more than frictional resistance when the core plug is introduced into the core, but the interlocking engagement of the ribs with the core olfers materially increased resistance to withdrawal, thus locking the core plug in place.

The saving in material which is an incidental advantage of the method and construction is very significant, amounting to 15% to 20% of the total of the metal formerly required.

In the drawings:

FIG. 1 is a view in end elevation of a core plug embodying the invention.

FIG. 2 is a view of the core plug in side elevation with portions broken away to the section 22 in FIG. 1.

FIG. 3 is a view of the improved core plug in perspective.

FIG. 4 is a plan view of the strip from which the blanks are stamped in the practice of the invention.

FIG. 5 diagrammatically illustrates a modified practice in which the blanks are stamped on such close centers as to have four flat sides instead of merely two.

FIG. 6 is a view similar to FIG. 1 showing the modified core plug produced by the practice diametrically illustrated in FIG. 5.

In general, the core plug is of a well known type shown in the expired patent to Brown 1,919,769. It is a cupshaped metal member having a bottom wall 10 and a side wall 11 peripherally flanged at 12. The bottom wall has an integral sleeve at 13 which receives the core shaft or mandrel. The side wall has ribs 14 which assure a snug fit of the core plug within the core.

In accordance with the present invention, the blanks from which the core plug is formed are cut with a circular die from a strip or web 15 of stock which is narrower than the over-all diameter of the otherwise circular blank 16 so that each of the blanks has opposed flattened sides at 17 as shown in FIG. 4. When the cupshaped core plug is formed in a die from the blank 16, each of the non-circular marginal portions 17 appears as a notch 170 in the side wall 11. In the preferred practice of the invention, these notches are intersected by two diametrically opposite ribs 14, thereby exposing a relatively sharp edge 20 at the end of the rib.

Two diametrically opposite sharp edges 20 are suificient to anchor the core plug securely in the core but, if desired, it is possible to cut the blanks 16-1 on closer centers than the blank 16 in FIG. 4, this resulting in forming four notched wall portions and four sharp terminal edges of the respective ribs which intersect the notches. FIG. 5 shows the closely coupled blanks 161 and the flattened nited States Patent 2,988,032 Patented June 13, 1961 2 arg s 1 h ch. upplementmar ins 7 to Provide. he additional anchor terminal edges. Unlike the blanks 16 of FIG. 4, which are cut with a conventional circular die, the blanks 161 of FIG. 5 will require a special die of a form to produce the flattened side margins 17.

Previous attempts to provide an interlock between core plugs and cores have involved extra stamping or forming operations. In addition to the saving of material, the advantage of the present invention lies in the fact that no extra operations are required. The ribs 14 would ordinarily be used in any event. However, even apart from the ribs, the edges 170, lying within the core, have very pronounced locking effect since, unlike the rounded junc ture of the side wall with the bottom, these edges are sharp and tend to interlock with the fiber of the core.

I claim:

1. A method of manufacturing a core plug from a generally circular blank, which method comprises the steps of cutting a sheet of stock to a width materially less than the diameter of the blank from which the plug is to be made, cutting a generally circular blank symmetrically from said sheet of stock, whereby the generally circular blank has its otherwise circular outline interrupted at diametrically opposite sides where the diameter of the blank exceeds the width of the sheet of stock, forming the resulting blank into cup shape, the resulting cup shape having side wall portions which are generally cylindrical and of substantially uniform height except at the diametrically opposite sides where the width of the stock was less than the diameter of the blank, said walls being arcuately notched at said sides, and the original margins of the sheet of stock forming the margins of the cup shaped blank at the notches thereof, forming marginal portions of the cylindrical side walls outwardly in the form of arcuate flanges intervening between said notched side wall portions, and spaced by said intervening side wall portions, and downwardly deforming side wall portions in registry with the notches therein to form ribs having relatively sharp terminal margins ending in the notches of the side walled portions.

2. A method of manufacture of core plugs from a generally circular blank, which method comprises the steps of cutting successive blanks of like dimensions from a strip of stock narrower than the diameter of any blank, whereby each blank has generally circular margins cut from said strip and non-circular margins formed by the edges of the strip, and forming each blank to cup shape with wall portions notched at the margins of the blank which constituted the original margins of the strip from which the blank was cut, together with the further method step of forming ribs in a wall portion of the cup-shaped core plug having end margins exposed at the notches in said wall portion.

3. A method of manufacture of core plugs from a generally circular blank, which method comprises the steps of cutting successive blanks of like dimensions from a strip of stock narrower than the diameter of any blank, whereby each blank has generally circular margins cut from said strip and non-circular margins formed by the edges of the strip, and forming each blank to cup shape with wall portions notched at the margins of the blank which constituted the original margins of the strip from which the blank was cut, together with the further step of flanging outwardly the unnotched marginal wall portions of each blank whereby each cup-shaped product has a generally circular flange interrupted by notches extending into side wall portions thereof.

(References on following page) ReferencesvCited in the file of this patent UNITED STATES PATENTS Withington Jan. 21, 1919 Fine Aug. 7, 1928 5 Hothersall Jan. 5, 1932 Ellison May 17, 1932 Lippitt et a1. Nov. 14, 1933 Christman Nov. 10, 1936 Bebie Apr. 9, 1940 Janisch Jan. 13, 1942 FOREIGN PATENTS Canada Feb. 26, 1952 Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE CF CORRECTION Patent No: 2,988,032 June 13 1961 Marvin Co Voissem It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent. should read as corrected below.

Column 2, line 37, for "downwardly" read outwardly Signed and sealed this 7th day of November 1961.,

SEA L) Attest:

ERNEST W. SWIDER DAVID L. LADD Commissioner of Patents USCOMM-DG 

